The appearance of coloured fabrics, e.g., clothing, bedding, household fabrics like table linens is one of the areas of concern to consumers. Indeed, upon typical consumer's uses of the fabrics such as wearing, washing, rinsing and/or tumble-drying of fabrics, lead to changes in fabric appearance, which is at least partly due to loss of colour shade intensity, fidelity and color definition.
Such a problem of colour loss is even more acute in laundry treatment after multiwash cycles, especially for dark colours, such as blacks, reds, blues, and greens.
Several mechanisms have been speculated upon for colour loss and various means have been proposed to prevent or reduce the extent of the loss or transfer of colour. For example, colour fixatives, known in the dyeing industry have been proposed, as have agents (such as PVP) to hold colour materials in solution to prevent re-deposition or to prevent abrasion between fibers. It has also been suggested to add bleaching agents to wash liquor to bleach any dye that enters solution.
One cause of colour loss is the use of an inappropriate detergent composition. Thus, many manufacturers produce ‘colour care’ formulations that do not contain bleaches. Despite this, colour damage remains a significant problem in the eyes of consumers.
WO 00/15746 (P&G), filed 15th, September 1998, published 23rd March 2000, discloses fabric care compositions, which comprise low molecular weight polyamines for colour care. It is believed that the polyamines intercept peroxygen bleaching. A dye fixative may also be present in the compositions disclosed, as may an ‘abrasion reducing polymer’ such as the N-heterocyclic polymer PVP (see examples 50–53 in table XII).
In order to overcome these problems it has also been proposed to use self cross-linking agents, to treat the fabric. These are believed to form a protective matrix around the fibers of the fabric, which reduces fiber damage. It is believed that this structure restricts relative movement of the textile fibers and consequently reduces damage to the textile fibers during the laundering process. It is also believed that this reduces pilling and provides shrink resistance.
It is further believed that the structure prevents apparent colour loss by retarding damage to the fibers leading to a rough fiber surface which would give the appearance of colour lose due to a modification of the manner in which light is scattered from the fiber surface.
Laundry detergent compositions containing reactive polyamide-polyamine fabric treatment agents are known. The compositions are claimed to impart improved overall appearance to fabrics laundered using the detergent compositions, in terms of surface appearance properties such as pill/fuzz reduction and anti-fading. Other cationic self cross-linking agents are known.
Polyamine epichlorohydrin resins (PAE) are effective self cross-linking agents, which is known to reduce fiber damage. However under certain circumstances use of PAE can lead to changes in the appearance of dyed fabrics as regards their colour. There is a need to overcome this problem.
WO 98/12295 (P&G: published 1988) discloses the combination of dye fixing agents and amino-functional polymers to improve the colour appearance of laundered fabrics especially after multi-wash cycles. One possible mechanism of action is that the dye fixative locks the dyestuff to the surface preventing colour loss, while the amino functional polymer prevents bleaches having a detrimental effect on dyes. There is no suggestion in this document that there is any reaction between the amini-functional material and the dye fixative.